1. Technical Field
This application relates to the fields of mobile phones and computing devices, digital photographs, image processing, and food databases. In particular, this application relates to the use of the above-mentioned fields in a system for recording dietary intake and analyzing nutritional content.
2. Description of the Related Art
Dietary intake provides some of the most valuable insights for mounting intervention programs for prevention of chronic diseases like obesity, for example. However, accurate assessment of dietary intake is problematic. Emerging technology in mobile telephones (cell phones) with higher resolution images, improved memory capacity, and faster processors, allow these devices to process information not previously possible. Mobile telephones and PDAs (personal digital assistants), which are widely used throughout the world, can provide a unique mechanism for collecting dietary information that reduces the burden on record keepers. Indeed, a dietary assessment application on a mobile telephone would be of value to practicing dietitians and researchers.
The increasing prevalence of obesity among younger generations is of great concern and has been linked to an increase in type 2 diabetes mellitus. Accurate methods and tools to assess food and nutrient intake are essential in monitoring the nutritional status of this age group for epidemiological and clinical research on the association between diet and health. The collection of food intake and dietary information provides some of the most valuable insights into the occurrence of disease and subsequent approaches for mounting intervention programs for prevention.
With this growing concern for obesity, the need to accurately measure diet becomes imperative. Assessment among adolescents is problematic as this group has irregular eating patterns and has less enthusiasm for recording food intake. Early adolescents, ages 11 to 14 years, in particular, are in that period of time when the novelty and curiosity of assisting in or self-reporting of food intakes starts to wane and the assistance from parents is seen as an intrusion. Dietary assessment methods need to continue to evolve to meet these challenges. There is recognition that further improvements will enhance the consistency and strength of the association of diet with disease risk, especially in light of the current obesity epidemic among this group.
Preliminary studies among adolescents suggest that innovative use of technology may improve the accuracy of diet information from young people. PDAs are ideal as a field data collection device for diet assessment; however, there have been problems when deploying these types of devices if one does not understand the user and the environment in which the device be deployed. Minimal training using mobile devices may improve the accuracy of recording.
The assessment of food intake in adolescents has previously been evaluated using more traditional methods of recording, i.e., food record (FR), the 24-hour dietary recall (24HR), and a food frequency questionnaire (FFQ), with external validation by doubly-labeled water (DLW) and urinary nitrogen. Currently, there are too few validation studies in children to justify one particular method over another for any given study design.
A review of some of the most popular dietary assessment methods is provided below. This review demonstrates the significance of the mobile system of the present disclosure which can be used for population and clinical based studies to improve the understanding of dietary exposures among adolescents.
24-Hour Dietary Recall
The 24-hour dietary recall (24HR) consists of a listing of foods and beverages consumed the previous day or the 24 hours prior to the recall interview. Foods and amounts are recalled from memory with the aid of an interviewer who has been trained in methods for soliciting dietary information. A brief activity history may be incorporated into the interview to facilitate probing for foods and beverages consumed. The Food Surveys Research Group (FSRG) of the United States Department of Agriculture (USDA) has devoted considerable effort to improving the accuracy of this method.
The major drawback of the 24HR is the issue of underreporting of the food consumed. Factors such as obesity, gender, social desirability, restrained eating and hunger, education, literacy, perceived health status, age, and race/ethnicity have been shown to be related to underreporting. For example, significant underreporting of large food portions is found when food models showing recommended serving sizes were used as visual aids for respondents. Given that larger food portions have been observed as occurring over the past 20 to 30 years this may be a contributor to underreporting and methods to capture accurate portion sizes are needed. In addition, youth, in particular, are limited in their abilities to estimate portion sizes accurately. The most common method of evaluating the accuracy of the 24HR with children is through observation of school lunch and/or school breakfast and comparing foods recalled with foods either observed as eaten or foods actually weighed. These recalls have demonstrated both under-reporting and over-reporting, and incorrect identification of foods.
The Food Record
The 24HR is useful in population based studies; however, the preferred dietary assessment method for clinical studies is the food record. For the food record, participants are asked to record all food and beverages consumed throughout a 24-hour period. Depending on the primary nutrient or nutrients, or foods of interest, the minimum number of food records needed is rarely less than two days. Training the subjects, telephoning with reminders for recording, reviewing the records for discrepancies, and entering the dietary information into a nutrient database can take a large amount of time and requires trained individuals.
The food record is especially vulnerable to underreporting due to the complexity of recording food. It has been shown that 10-12 year old children significantly underreport total energy intake (TEI) when the intake is compared against an external marker, doubly-labeled water. In addition, as adolescents snack frequently, have unstructured eating patterns, and consume greater amounts of food away from the home, their burden of recording is much greater compared to adults. It has been suggested that these factors, along with a combination of forgetfulness and irritation and boredom caused by having to record intake frequently may be contributing to the underreporting in this age group. Dietary assessment methods perceived as less burdensome and time consuming may improve compliance.
Portion Size Estimation
Portion size estimation may be one contributor to underreporting, in general. For example, it has been found that training in portion size estimation among 9-10 year olds significantly improves estimates for solid foods measured by dimensions or cups, and liquids estimated by cups. Amorphous foods are estimated least accurately even after training and other foods still present significant errors.
Evaluation of Dietary Assessment Methods
The number of days needed to estimate a particular nutrient depends on the variability of the nutrient being assessed and the degree of accuracy desired for the research question. Most nutrients require more than four days for a reliable estimate. However, most individuals weary of keeping records beyond four days which may decrease the quality of the records.
Another challenge in evaluating dietary assessment methods is comparing the results of the dietary assessment method to some measure of “truth.” This is best achieved by identifying a biomarker of a nutrient or dietary factor. The underlying assumption of a biomarker is that it responds to intake in a dose-dependent relationship. The two methods that have widest consensus as valid biomarkers are DLW for energy and 24-hour urinary nitrogen for protein intake. A biomarker does not rely on a self-report of food intake, thus theoretically the measurement errors of the biomarker are not likely to be correlated with those of the dietary assessment method. Other biomarkers collected from urine samples may include potassium and sodium. Some plasma or serum biomarkers that have been explored are levels of ascorbic acid for vitamin C intake, and 13-carotene for fruits and vegetables or antioxidants. These latter markers are widely influenced by factors such as smoking status and supplement use, thus their interpretation to absolute intake is limited.